The present invention relates generally to methods and apparatus utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a hydraulic control system for downhole tools.
It would be desirable to be able to operate selected ones of multiple hydraulically actuated well tools installed in a well. However, it is uneconomical and practically unfeasible to run separate hydraulic control lines from the surface to each one of numerous well tool assemblies. Instead, the number of control lines extending relatively long distances should be minimized as much as possible.
Therefore, it would be highly advantageous to provide a hydraulic control system which reduces the number of control lines extending relatively long distances between multiple hydraulically actuated well tools and the surface. The hydraulic control system would preferably permit individual ones of the well tools to be selected for actuation as desired. The selection of well tools for actuation thereof should be convenient and reliable.
Furthermore, it would be desirable to provide methods of controlling operation of multiple well tools, and it would be desirable to provide well tools which maybe operated utilizing such a hydraulic control system.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a hydraulic control system is provided which solves the above problem in the art. Methods of controlling operation of multiple downhole tools, and well tools which may be controlled using such methods, are also provided by the invention.
In one aspect of the invention, a hydraulic control system is provided which includes multiple control modules for controlling operation of multiple well tool assemblies. Each of the control modules is connected to a corresponding one of the well tool assemblies. One or more flowpaths extending to a remote location, such as the earth""s surface, are connected to each of the control modules.
The flowpaths are used to transmit fluid pressure to the control modules. Pressure on the flowpaths is used to select from among the well tool assemblies for operation thereof, and to operate the selected well tool assemblies. In one embodiment, pressure is applied to two of the flowpaths to select a well tool assembly, and pressure is applied to a third flowpath and/or one of the other two flowpaths to operate the selected well tool assembly.
In another aspect of the invention, each of the control modules includes a member which is displaced in response to pressure on one or more of the flowpaths. All of the members are displaced when appropriate pressure is on the flowpaths. For example, in one embodiment, pressure is applied alternately and repeatedly to two of the flowpaths to displace all of the members simultaneously. The members are each uniquely configured, so that only one of the well tool assemblies is selected at a time.
In yet another aspect of the invention, pressure on one of the flowpaths may be used to synchronize the members. Pressure on the flowpath causes each of the members to cease displacing in response to pressure on other flowpaths, when the member reaches a certain predetermined position. In this manner, all of the members may be placed in the predetermined position in the corresponding control module, at which point all of the members are synchronized with each other.
In still another aspect of the invention, the control modules may be configured so that a minimum pressure on a flowpath is required to displace each of the members past a certain position. Each of the members displaces up to the certain position when a lower pressure is used, but ceases displacing in response to the lower pressure when the position is reached. Thus, all of the members may be placed in the position by displacing the members using the lower pressure.
In a further aspect of the invention, a flowpath in communication with a tubular string or an annulus downhole may be placed in fluid communication with one of the flowpaths extending to the remote location using one of the control modules. In this manner, pressure in the tubular string or annulus may be selectively monitored at the remote location.
In a still further aspect of the invention, well tool assemblies are provided which are operable using the control systems disclosed herein. One well tool assembly is a valve, which is openable and closable by application pressure on the flowpaths extending to the remote location. Another well tool assembly is a variable choke. The choke includes a ratchet mechanism permitting a flow area through the choke to be incrementally and repeatedly varied.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings.